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Biomedical subjects

R Kirsch

Publications and source records attributed to R Kirsch.

98 records · Page 6Linked to original sources
PubMedDate not supplied

New systematically active antimycotics from the beta-blocker category.

Candida albicans secretes phospholipases, which are considered to be one of the mediators of cell penetration. It is known that other phospholipases from mammalian cells can be inhibited by lipophilic beta-blocking structures. As the result of a synthesis programme of several years' duration, structures deriving from beta-hydroxyethylamines were introduced. In vitro and in vivo results with these compounds are presented in comparison with standard antimycotics. In combination with fluconazole, several of the compounds can prevent death in mice infected with lethal inocula of C. albicans. Histological examinations confirm the inhibitory effect of the beta-blocker-like structures on tissue penetration. The structures therefore constitute new antimycotics that are endowed with extensive in vitro effectiveness against fungi and also definite in vivo effects in the animal model.

Adrenergic beta-Antagonists↗
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Effects of different doses and durations of melatonin infusions on plasma melatonin concentrations in pinealectomized Syrian hamsters: consequences at the level of sexual activity.

The effect of different doses and durations of melatonin infusions on plasma melatonin concentrations has been studied in pinealectomized Syrian hamsters maintained under short photoperiod at either 7 degrees C or 18 degrees C. The effects of the infusions on plasma melatonin concentrations and on gonadal activity were compared. The results show that the minimal effective quantity of infused melatonin that induced gonadal atrophy was 40 ng/h at 7 degrees C and 20 ng/h at 18 degrees C. An infusion of 8 hr duration per day is necessary to inhibit sexual activity, while an infusion of 6 hr duration was ineffective. This finding suggests that the critical duration of melatonin infusion is between 6 and 8 hr. Despite the various doses of melatonin infused, plasma melatonin concentrations measured in the middle of the infusion period did not differ significantly from concentrations measured in intact animals. This finding suggests that the metabolism of infused melatonin increases as the dose of melatonin increases. Moreover, the different physiological effects observed after the various melatonin infusions cannot be explained by variations in plasma melatonin concentrations.

Animals↗
PubMedDate not supplied

Expression of daily torpor in the Djungarian hamster (Phodopus sungorus) is correlated with the testosterone-driven vasopressin content in the lateral septum.

In the Djungarian hamster (Phodopus sungorus), torpor bouts appear after exposure to short photoperiods (SP) for 11 weeks. Castration accelerates the occurrence of daily torpor when performed between the 1st week before and the 4th week after transfer to SP. In animals castrated 8 weeks before transfer to SP, daily torpor was observed nearly at the same time as in the control group. Vasopressin-immunoreactivity (VP-ir) in the lateral septum (LS) of the Djungarian hamster was examined. Dense VP-ir was seen in sexually active and in sexually inactive hamsters implanted with testosterone (T) capsules. No VP-ir could be detected in sexually inactive animals. Thus, the presence of VP-ir in the LS depends on circulating T levels. In control animals exposed to SP, complete disappearance of VP-ir in the LS was observed after 8 weeks. Castration on the day of transfer to SP reduced this period to 6 weeks. In these animals, the early occurrence of daily torpor is related to the quick disappearance of VP-ir in the LS. When castrated animals were maintained under long photoperiods the disappearance of VP-ir was not complete. However, VP-ir disappeared completely after transfer to SP. The results suggest that the SP message acts on daily torpor indirectly via testicular regression but also 'directly' via VP septal innervation.

Activity Cycles↗
PubMedDate not supplied

Effects of stimulated hip extension moment and position on upper-limb support forces during FNS-induced standing--a technical note.

This study explores the effects of active hip extension moment produced by electrical stimulation on the support forces the arms must exert through an assistive device during quiet erect standing with functional neuromuscular stimulation (FNS) in individuals with spinal cord injuries (SCI). A static sagittal plane biomechanical model of human standing was developed to predict the effects of stimulated hip extension moment and sagittal plane hip angle on the arm support necessary to maintain an upright posture. Two individuals with complete thoracic SCI were then tested while they stood with continuous stimulation to the knee and trunk extensors. The steady-state active extension moment exerted at the hip was varied by activating different combinations of hip extensor muscles with continuous stimulation while steady-state support forces applied to the arms and feet during standing were measured. The steady-state support forces imposed on the arms during quiet standing decrease with increased stimulated hip extension moment and are highly dependent upon hip flexion angle, as predicted by the biomechanical simulations. Experimentally, the combination of gluteus maximus and semimembranosus stimulation produced three times more steady-state hip extension moment than did stimulation of the gluteus maximus and adductor magnus. This resulted in a ten-fold decrease in body weight supported on the arms. More vertical postures (smaller hip flexion angles) improve the effectiveness of the hip extensor muscles in reducing the support forces placed on the arms. A single Newton-meter of stimulated hip extension moment with the hips fixed at 5 degrees of flexion results in almost five times the reduction in arm support forces as with the hips at 20 degrees. To minimize the forces applied by the arms on an assistive device for support while standing with FNS, these preliminary results suggest that (1) efforts should be made to assume the most erect postures possible and (2) muscles and stimulation paradigms that maximize active hip extension moment should be chosen.

Adult↗
PubMedDate not supplied

Treatment of nematodiasis in poultry and game birds with fenbendazole.

Administration of 100 ppm fenbendazole to 661 pheasants (Phasianus colchicus colchicus) and 25 partridges (Perdix perdix) for 4 days reduced natural infection with Syngamus trachea and/or Capillaria obsignata and in some cases with Heterakis spp. by more than 90%. A 5-day administration of feed medicated with 30 or 60 ppm fenbendazole resulted in almost 100% efficacy against natural C. obsignata and Heterakis gallinae infection in 343 pullets. The treated pullets were kept under poor hygienic conditions, resulting in slight reinfection, which manifested itself in immature nematode stages at autopsy and in a slight excretion of nematode eggs in individual cases. Fenbendazole treatment effected the clinical recovery of the stocks within a few days and was very well tolerated.

Animals↗